Key Points

These latest results show that over half of patients in the study did not report moderate or marked side effects at any point, and that most side effects reduced over time.

The number of side effects reported per person were fewer in the partial breast and reduced dose groups compared with the WBRT group.

The average number of moderate or marked side effects reported by patients with breast cancer is lower if they are treated with radiotherapy to part of the breast or a reduced dose to the whole breast, rather than with standard whole breast radiotherapy (WBRT), according to new findings presented at the 11th European Breast Cancer Conference (EBCC-11) (Abstract 3).

The IMPORT LOW study of 2016 women in 41 centers in the UK has already shown that partial breast and reduced dose radiotherapy was as effective as WBRT in controlling cancer at 5 years, and women in the partial breast and reduced dose groups reported fewer side effects, including less change in the appearance of the breast.

These latest results—which focus predominantly on side effects affecting the breast and body image reported during the 5 years following radiotherapy—show that over half of patients in the study did not report moderate or marked side effects at any point, and that most side effects reduced over time. The number of side effects reported per person were fewer in the partial breast and reduced dose groups compared with the WBRT group.

Dr. Indrani Bhattacharya, a clinical research fellow at the Institute of Cancer Research’s Clinical Trials and Statistics Unit, said, “The findings from this study are reassuring for women who are offered either whole-breast or partial-breast radiotherapy using this technique of radiotherapy, which is simple to deliver and already available in centers worldwide.”

“This new information will help doctors discuss the risks and benefits of this type of radiotherapy with patients and may improve shared decision­making, as well as enabling them to tailor treatment for individual patients.”

More on IMPORT LOW

The IMPORT LOW study randomized women to receive standard radiotherapy at a dose of 40 Gy to the whole breast (the control group); 36 Gy to the whole breast and 40 Gy to the part of the breast that contained the original tumor (reduced dose group); or 40 Gy only to the site of the original tumor (partial breast group). The radiotherapy was given using hypofractionated intensity modulated radiotherapy (IMRT).

More than half of the women (1,265) took part in the substudy that looked at patient-reported outcomes. At the start of the study; after 6 months of treatment; and 1, 2, and 5 years after radiotherapy, the women were asked about adverse side effects, such as a hardening of tissue, pain, oversensitivity of the treated area, and build­up of fluid.

Most of the side effects reported by the women related to changes affecting the breast, and the most-reported side effect was “overall change in breast appearance”.

The researchers found that women were more likely to report adverse side effects if they were younger, had larger breasts, had a larger volume of breast tissue removed at surgery, if the cancer had spread to any of their lymph nodes, and if, at the start of the study, they were feeling anxious or depressed.

“Now that we can identify these patients who are at higher risk of reporting side effects, this knowledge can be discussed with patients, may modify treatment, and enable doctors to put in place more personalized and frequent monitoring if necessary. For example, patients with higher levels of anxiety and depression could be offered psychosocial support at the start of treatment, although we do not know from this study whether this would reduce the reporting of side effects,” said Dr. Bhattacharya.

“We have previously reported that partial-breast radiotherapy is as effective as WBRT with similar or fewer side effects over 5 years and can be safely delivered in a selected group of patients with low-risk breast cancers. This new analysis shows that patients requiring WBRT can be reassured about the low risk of side effects affecting the breast and body image. The technique of radiotherapy used in IMPORT LOW is easy to implement and deliver as the equipment and expertise is available in all centers worldwide.”

The IMPORT LOW trial is the largest randomized trial to study the use of IMRT to deliver partial or low dose breast radiotherapy compared to WBRT, and has provided the largest complete set of patient-reported outcomes data for several points in time over 5 years.

“Patient-reported outcomes are very important for both women and clinicians as they describe side effects from the patients’ perspective and allow us to see the long-term effects of treatment as recorded by the patient. We know from this study and other studies that patients report more side effects compared to doctors. This means that if we did not assess side effects using patient-reported outcomes, then the impact of the treatment-related side effects on the patient may be underestimated,” concluded Dr. Bhattacharya.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.